But the administration also called out Hamas for using UN facilities to hide weapons — echoing a charge Israel has been making since the conflict began.

“We are extremely concerned that thousands of internally displaced Palestinians who have been called on by the Israeli military to evacuate their homes are not safe in UN- designated shelters in Gaza,” said White House National Security Council spokeswoman Bernadette Meehan.

“We also condemn those responsible for hiding weapons in United Nations facilities in Gaza.”

Israeli tank shells slammed the UN school packed with refugees hours before airstrikes hammered a market crowded with shoppers, killing at least 16 and wounding more than 200 in another deadly day of escalating violence.

Gaza officials said at least 17 people were killed and about 90 wounded in the strike at the school in the Jebaliya refugee camp.

And while the United States and UN decried the attack, the Israeli military said it had returned fire only after soldiers were targeted by mortar rounds launched from the area surrounding the school.

We are extremely concerned that thousands of internally displaced Palestinians who have been called on by the Israeli military to evacuate their homes are not safe in UN- designated shelters in Gaza.

- Bernadette Meehan, White House National Security Council spokeswoman

Israeli officials have repeatedly accused Hamas of deliberately integrating fighters among civilian populations and using UN facilities as weapon depots.

Hamas militants fired 84 more rockets from Gaza at Tel Aviv, Jerusalem and other targets in Israel Wednesday, and three more Israeli soldiers were killed when a booby-trapped house collapsed after they discovered an entrance to a tunnel inside.

That raised the number of Israeli soldiers killed to 56. Three Israeli civilians also have been killed since the July 8 start of fighting.

In all, Gaza officials said 1,359 Palestinians have been killed, including 114 on Wednesday.

UN Secretary-General Ban Ki-moon called Wednesday’s strike on the school “outrageous” and “unjustifiable,” and demanded an immediate cease-fire.

Israel has been warning civilians by phone and leaflet to leave dangerous areas ahead of strikes on militant targets.

The head of the Israeli army’s southern command said Israel was “a few days” away from destroying the 32 Hamas tunnels it has located so far.

The House of Representatives, meanwhile, passed a resolution denouncing Hamas’ use of human shields as a violation of international humanitarian law.